The overall objective of this project is to determine the normal developmental profile of surfactant production in the first few hours and days after delivery. During the coming grant period we will focus our attention on a study of surfactant release from newborn rabbit lung slices. We will examine the effects of a number of agents on surfactant secretion in this mode. These will include adrenergic and cholinergic agonists and antagonists; colchicine and cytochanlasin-B; agents which inhibit secretion by interfering with the microtubule or microfilament systems; the calcium ionophore A23187; and prostaglandins. Newborn rabbits will be injected with (methl-3H)choline and will be sacrificed 4 hours later. The lungs will be rapidly removed and perfused free of blood elements. The lung will be chopped into slices, the slices will be washed using a technique developed in this laboratory and release of surfactant from the slices will be measured. By measuring the rate of corporation of choline into phosphatidylcholine we will also be able to examine the effect of perturbations of secretion on the rate of synthesis.